As semiconductor devices become increasingly smaller and highly integrated, the line spacing between signal lines decreases, which causes an increase in the coupling capacitance between adjacent signal lines on a semiconductor device. Such coupling capacitance changes the delay time of a circuit and generates noise. Accordingly, methods for analyzing crosstalk between signal lines of a semiconductor device are very useful for determining if potential crosstalk problems exist before the device is actually fabricated. In this way, the circuit design can be modified or other actions can be taken, if necessary, with respect to signal lines that may provide potential crosstalk problems.
To analyze crosstalk of a circuit, signal lines are classified as either “aggressors” or “victims”. The “aggressors” are further classified as either “true aggressors” (which influence the victims) or “false aggressors” (which do not influence the victims). There are two types of aggressor classification methods known in the art, referred to as a functional classification method and a temporal classification method.
With a conventional functional classification method, “aggressors” are classified as “true aggressor” or “false aggressors” depending on whether or not the logical status of signals of a victim and aggressor affects noise and delay time of signals of other signal lines. More specifically, “true aggressors” affect their corresponding “victims” in terms of noises and delay times based on logic status thereof, whereas “false aggressors” do not affect their corresponding “victims” as such. The conventional functional aggressor classification method has a disadvantage in that the classification process is time consuming because all aggressors are classified as true or false aggressor after all the aggressors in a circuit are backward searched.
With a conventional temporal classification method, all aggressors presented are classified by temporally overlapping when a signal is presented at a signal line of a victim and calculating a minimum signal transition time and a maximum signal transition time that signals of the aggressors and victims start to transition. With this method, every aggressor that is overlapped with a victim in timing are classified as “true aggressors”. The conventional temporal aggressor classification method has a disadvantage in that there is a possibility of erroneously classifying an aggressor (which will not cause any problem in a circuit) as a true aggressor, because such method does not take into consideration possible temporal overlap between aggressors.
The present invention provides improved classification methods that provide solutions to the problems associated with conventional functional and temporal aggressor classification methods.